The invention relates to a hydraulically controlled, pneumatic impact implement and its application in a tool such as a cutter or hammer. It relates particularly to a pneumatic actuator having its piston rod protruding out of the actuator cylinder and serving to impart heavy shocks onto an object to be cut or compressed.
There exist many pneumatic tools such as hammers, riveters, pavement breakers and others, wherein a free-floating piston is oscillatingly and rapidly moved by valve control, and impacts on the rear end of a tool such as a chisel or hammer. On the other hand, there exist long-stroke pile drivers wherein both weight and pneumatic force are combined to impart a strong blow onto the pile head and to drive the pile into the ground.
Up to now all known pneumatic cylinders are designed to be supplied with compressed air through a valve at the far end, which expands with the outerward movement of the piston, whereby the actual force on the piston at the end of the stroke has diminished to the exhaust pressure. In the aforementioned applications this is irrelevant, since the piston is accelerated during its stroke in the cylinder so as to act on the tool by its velocity momentum. However, there exist tools which require a strong force throughout the piston movement such as, for instance, cutters, and it is the object of the present invention to provide a long-stroke, pneumatic impact implement capable of exerting strong pressure of substantially uniform magnitude during the entire stroke of the piston.
It is another object of the invention to provide a pneumatic implement of simple construction and, accordingly, at low cost.
And it is a final object to provide an implement which will require little maintenance due to its few moving components.